code: def message_func(self, edges):
      # message UDF for equation (3) & (4)
      return {"z": edges.src["z"], "e": edges.data["e"]}
  
imports: import os
  import torch
  import torch.nn
  import torch.nn.functional
  from dgl.nn.pytorch import GATConv
  import networkx
  from dgl import DGLGraph
  from dgl.data import citation_graph
  import time
  import numpy
label_desc: Use image node_id 4 for calling the GATLayer obj's underlying member method code with example usage: obj.message_func(edges) and returns: dict